Scientists Outline Research on a Rare Case of AIDS

BOSTON, Feb. 24 - The researchers whose findings led the New York City health department to warn of a rare and possibly virulent strain of H.I.V. defended on Thursday their decision to notify city officials, saying the virus presented a serious threat to public health.

Giving a detailed account of their investigation for the first time at a scientific meeting here, the researchers said their discovery of the potentially more aggressive strain in a New York City man with multiple sexual partners was reason enough to sound the alarm.

Dr. David Ho, director of the Aaron Diamond AIDS Research Laboratory in Manhattan, which first identified the possible new strain, said: "I think we have a unique convergence of a very drug-resistant virus, and this infection was very, very rapid. And this man has many, many sexual partners."

While the broad outlines of the case have been known since Feb. 11, when Dr. Thomas R. Frieden, the New York City health commissioner, announced the findings at a news conference, Dr. Ho was given the opportunity by organizers of the 12th Annual Retrovirus Conference to present his team's latest findings.

In a special symposium arranged to deal with the issues raised by the New York case, Dr. Ho presented his case to thousands of the world's top AIDS experts at the Hynes Convention Center. He said it was unique not only among all those the Aaron Diamond Center had ever seen, but also among all the cases cataloged in the laboratory at Los Alamos, which collects data of the gene sequences and other molecular biology information of H.I.V. isolates from around the country.

He said that while it was still not known whether the New York case was isolated or part of a cluster, alerting the health department was the right thing to do. "That is a decision we stand by today," he said.

Some scientists and members of gay rights groups have criticized the disclosure as premature and unnecessarily alarmist, but there is little doubt that the strain of H.I.V. was resistant to three of the four licensed classes of antiretroviral drugs used to combat the AIDS virus.

Although drug-resistant AIDS viruses are thought to be less potent than those that respond to drugs, Dr. Ho and a colleague, Dr. Martin Markowitz, said that may not be true in this case. In fact, they said, the virus replicated well in the laboratory, which they called "worrisome."

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The researchers' report outlined the steps they had taken to determine whether the patient progressed rapidly from H.I.V. infection to AIDS because of an immune system problem or because the virus was particularly aggressive.

Scientists can test for a number of genetic markers that indicate whether a patient is unusually susceptible to such a quick progression. Dr. Ho's team reported that it had found none of the key indicators that usually signal rapid progression of the virus. Dr. Ho said they had several more tests yet to run. But even when all the tests are complete, he said, there will still be room for doubt. "The scientific community simply doesn't know enough about genetic markers for disease progression," Dr. Ho said in an interview before the presentation. "There could be other markers that we cannot look at, so we can never exclude genetics, because the knowledge is incomplete."

It takes on average about 10 years for a person to develop AIDS after infection. But the range is wide: Some people may develop AIDS after about 20 years, while others get the disease within a year or so.

The team cited other research showing the likelihood of progression to AIDS 6 months after infection to be 7 in 10,000, and in 12 months 45 in 10,000. That means, the scientists said, that the New York City man whose case led to the investigation would be in the top 0.5 percentile.

The patient is a 46-year-old gay man who tested positive for H.I.V. in December. Another test showed that the man had antibodies to H.I.V., indicating that he had been infected for more than three months, but less than 20, Dr. Ho said.

He said the patient's description of his sexual history led the researchers to believe that infection probably occurred in October. In particular, the man described two nights when he took crystal methamphetamine and was more vulnerable to infection because he was the recipient of unprotected anal sex, which was not his usual practice, Dr. Ho said.

The man began to feel ill in early November. While he stopped using crystal meth, he continued having sex with about 10 partners until the end of December, the report said. By early February, the man had lost at least nine pounds and had symptoms that met the definition of AIDS.